Why is 20-mph needed?

The following image shows why 20-mph is the best speed while driving through built up areas and where we live, work and walk.


Chart showing stopping distances at 30mph and 20mph 

Distance from a driver noticing someone potentially in the path of their vehicle  Driver speed at 30mph  


Driver speed at 20mph 


0-6 metres  Likely to kill  Likely to injure 
6-12 metres  Likely to kill  Likely to hurt 
12-23 metres  Likely to seriously injure, less likely to kill  The driver stops without hitting the child.